Creating a runtime

Since Fetch relies on ConcurrentEffect from the cats-effect library, we'll need a runtime for executing our effects. We'll be using IO from cats-effect to run fetches, but you can use any type that has a ConcurrentEffect instance.

For executing IO we need a ContextShift[IO] used for running IO instances and a Timer[IO] that is used for scheduling, let's go ahead and create them, we'll use a java.util.concurrent.ScheduledThreadPoolExecutor with a couple of threads to run our fetches.